Linkage energy return shoe

ABSTRACT

The key feature of the “linkage energy return shoe” is a compressible sole comprising a sole linkage which constrains the upper shoe plate to not tilt, in one embodiment, and to follow a controlled compression path, in general. A consequence of the anti-tilt feature inherent in the sole linkage is that a spring located anywhere in the sole resists sole compression at both the toe section and the heel section. Thus, one or two springs or stops suffice, and the modular design makes it a simple matter to change springs to tune the bow shoe to an individual&#39;s weight and gait and to change shoe and ground plates for different size feet. The spring system can easily give a constant force curve, a linear force curve, or any force curve in between—thereby permitting faster running for a given maximum force and thereby reducing impact injuries.

This application is a continuation-in-part of the following: (1) co-pending U.S. application Ser. No. 10/610,629 for a “Full Energy Return Shoe” filed on Jul. 2, 2003, (2) U.S. provisional application Ser. No. 17513 USPTO 60/505,431 for a “Guided Bow Shoe” filed on Sep. 25, 2003, and (3) U.S. provisional application Ser. No. 19587 USPTO 60/491970 for a “Full Energy Return Shoe” filed on Aug. 4, 2003.

BACKGROUND

This invention is a linkage energy return shoe. It comprises various embodiments of an “energy return linkage,” referred to herein as a “sole linkage,” attached to upper and lower sole plates along their full lengths. The sole linkage constrains relative motion of the upper and lower sole plates by limiting or eliminating relative tilting and by controlling or eliminating relative longitudinal motion. These constraints result in foot impact energy being stored in springs regardless of whether the force acts on the front or rear of the sole. That is, both toe and heel impact energy are used or returned during toe-off. These springs are coupled to links or vertices of the linkage and are designed to achieve an optimal ground reaction force curve of the shoe on the ground—varying from linear to constant force curves. Most of the volume of the sole linkage is free space which distinguishes it from conventional running shoes which have solid, foam-filled structure of conventional running shoes.

A first type of sole linkage is referred to herein as a “guided p-diamond linkage” in that its linkage comprises a diamond shaped part, as well as overlapping parallelogram parts. The second type of sole linkage is referred to herein as a “p-linkage” in that its sole constraint is due to a parallelogram linkage which constrains the top of the sole to be parallel to the bottom of the sole, as it compresses. The shoes based on these two types of linkages are referred to herein collectively as “linkage shoes,” and particularly as the “guided p-diamond shoe” and the “p-linkage shoe.” The springs of the linkage shoe act directly between elements of the sole linkage. Another embodiment of the invention is a suspended linkage shoe, in which the top of the sole linkage is suspended from a bow spring, and it is referred herein as the “bow shoe.”

The p-diamond shoe constitutes an improvement of U.S. Pat. No. 6,684,531 of Rennex issued on Feb. 3, 2004, which discloses a p-diamond linkage and which incorrectly claims that this p-diamond linkage constrains the deflection of the sole to only the vertical degree of freedom The improved p-diamond shoe herein adds a guide element to achieve the claimed constraint. The new linkage herein is referred to as the guided p-diamond linkage. Extensive prior art is discussed in this earlier patent of Rennex, but it is not considered to be relevant to the new or old matter herein. In addition to the above improvement in the earlier patent, the current invention expands the scope of the earlier invention to a related and more extensive family of linkages in which the links rotate in the “up/forward” plane. Also, this invention increases the scope of these linkages to include asymmetric linkages, e.g., where the toe sole is thinner than the heel sole—in which case the linkages fall into the general class of quadrilaterals, of which the parallelogram in a particular example.

SUMMARY

The key feature of the linkage shoe is a compressible sole comprising a sole linkage which constrains the upper shoe plate not to tilt as it moves vertically up and down with respect to the ground plate. An advantage is that a minimal number of springs and stops (even one spring) of any kind can be used (without need of a spring guide). These springs and stops can easily be modular and replaceable to fit the performance requirements of an individual for walking and running. A consequence of the anti-tilt feature inherent in the sole linkage is that a spring located anywhere in the sole resists sole compression at both the toe section and the heel section. Thus, one or two springs or stops suffice, and the modular design makes it a simple matter to change springs to tune the bow shoe to an individual's weight and gait and to change shoe and ground plates for different size feet. The spring system can easily give a constant force curve, a linear force curve, or any force curve in between—thereby permitting faster running for a given maximum force and thereby reducing impact injuries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows side views and a front view of the guided p-diamond linkage embodiment of the invention which is a non-tilting compressible structure called a sole linkage.

FIG. 2 shows schematic multiple views of the guided p-diamond linkage.

FIG. 3 shows a side views which discuss a constant force curve, which depict external springs, and which show a guided bow linkage.

FIG. 4 shows various means to attach a foot to the linkage shoe.

FIG. 5 shows line-link side views of asymmetric versions of the guided p-diamond, wherein the simplified schematic presentation is called herein a “line-link view” in that lines represent links.

FIG. 6 shows a line-link side view of a guided p-diamond and front and side views of a half-height guided p-diamond.

FIG. 7 is a schematic side view of the bow shoe embodiment, with a shin-level bow spring and a compressible guided p-diamond sole.

FIG. 8 is a schematic front view of the bow shoe embodiment, with a shin-level bow.

FIG. 9 shows side views of the p-linkage embodiment of the invention which is a non-tilting compressible structure called a sole linkage.

FIG. 10 shows side views of the p-linkage at heel strike, mid-stance, and toe-off.

FIG. 11 shows side, top, and front views of the p-linkage.

FIG. 12 shows various types of springs and spring attachment means and locations.

FIG. 13 shows side views of various versions of the stretched-p embodiment of the p-linkage.

FIG. 14 shows line-link side views of a 2p-linkage, first with symmetric link lengths and second with asymmetric link lengths.

FIG. 15 show views of a hanging p-linkage.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 a, 1 b, and 1 c are schematic side views of one embodiment, guided p-diamond linkage 9 (described in detail later), of the main invention which is linkage energy return sole 12 (corresponding to linkage shoe 2, the general name herein for the corresponding shoe) and which compresses during foot strike and which returns thrust during toe-off. Again, linkage energy return sole 12 is a non-tilting compressible structure (linkage) for use in a shoe sole wherein the linkage provides the non-tilting constraint and an energy storage means gives energy return during walking and running. Energy return linkage 190 is the general name of the linkage which defines linkage energy return sole 12, and it corresponds here to guided p-diamond linkage 9. The particular embodiment of linkage energy return sole 12 shown is called guided p-diamond sole 8, here defined by guided p-diamond linkage 9. FIG. 1 a shows heel-strike, FIG. 1 b shows mid-stance with guided p-diamond sole 8 compressed, and FIG. 1 c shows toe-off. Runner's foot 1 is confined to the front section of upper frame 6 and to optional push-off frame 18 by shoe straps 22. The term runner is used herein to also mean wearer, in that linkage shoe 2 can also be used for walking. Again, the general term for the linkage which provides the critical “parallel top/bottom frame constraint” is linkage energy return sole 12 , of which p-diamond sole 8 is one embodiment.

Push-off frame 18 is one example of an optional push-off means, which achieves the following functions. (1) It always allows the runner to flex her metatarsal joint to lift her heel and push off of her toe at toe off. (2) It prevents the runner's toe from twisting out of the foot attachment means at the toe section by constraining the rear part of the runner's foot to lift vertically with respect to the rear part of upper frame 6. (3) It can be used as part of a mechanism to lift the rear part of upper frame 6 to contact the runner's heel during swing phase. Push-off frame 18 may extend around the runner's heel a variable distance above the bottom of the heel, or it may extend only part way back toward the heel. It may also be a plate located at the bottom of the runner's heel and mid-foot, which plate may be have holes or voids of variable size. Another example of a push-off means is a largely vertically-oriented sliding guide, not shown, which is attached to upper frame 6, and which has a sliding element attached to the heel of linkage shoe 2 via a sliding element, again not shown—but obvious to one of ordinary skill in the art. Yet another example of a push-off means would improve the stability of push-off frame 18 by adding a pair of hinged plates hingeably connecting the back of upper frame 6 with the back of push-off frame 18. Runner's foot 1 is attached to cover plate 21 by shoe straps 22. Cover plate 21 is fixedly attached to upper frame 6 to form an upper sole plate, and cover plate 21 is fixedly attached to lower frame 4 to form a lower sole plate. Optional push-off frame 18 is hingeably connected to upper frame 6 below or on the outsides of the location of the metatarsal joint of runner's foot—thereby allowing the runner to push off naturally at toe-off. Lower frame 4 may incorporate ground plate rocker 30 and ground plate curved toe 32 to optimize the energy return of linkage shoe 2 (by permitting greater forward tilt at toe-off).

FIG. 2 shows three views of guided p-diamond shoe 11. Additional elements shown in FIG. 1, but not yet described will be described now. Many of the structural aspects of this particular embodiment apply to the numerous other embodiments described herein, such as the skeletal nature of guided p-diamond linkage 9. Side-view FIGS. 2 a and 2 b show guided p-diamond shoe 11 expanded and compressed. FIG. 2 c is a front view, and FIG. 2 d is a top view. Guided p-diamond shoe 11 comprises one or more (two here, one on either side) guided p-diamond linkages 9, rigidly connected by cross beams 13, and optionally covered by cover plates 21 on the top and the bottom. Cover plate 21 need not cover the entire area of lower frame 4; it could simply be made of a durable material such as vibram or hard rubber bonded to the length and cross beam elements of lower frame 4.

Guided p-diamond linkage 9 comprises four diamond links 10, one top length link 23, one center length link 24, one bottom length link 25, as well as two end links 14—all of which are hingeably connected in the depicted configuration by link hinges 16. Top length link 23 and bottom length link 25 optionally extend beyond link hinges 16 on either end, but the functional parts for guided p-diamond linkage 9, those which cause the critical constraint of guided p-diamond linkage 9 to maintain upper frame 6 and lower frame 4 parallel, require only the sections between link hinges 16. Another motion constraint is for upper frame 6 to not move longitudinally forward or backward with respect to lower frame 4, during compression. This constraint is provided by mid-link front vertex guide 71, rigidly attached to center length link 24 and extending horizontally to the left in FIG. 2 b, which guides the forward most link hinge 16 to follow a horizontal path while p-diamond linkage 9 collapses and expands. That is, this guided constraint ensures that center length link 24 stays precisely in the center between top length link 23 and bottom length link 25. As long as this center position is maintained, the bearing force of front mid link hinge 16 on mid-link front vertex guide 71 is minimal. This minimal guiding force is a key advantage of guided p-diamond linkage 9 over other possible linkages.

In total, all these links form a 9-bar linkage (plus mid-link front vertex guide 71), which constrains upper frame 6 to move vertically (with no tilting) with respect to lower frame 4. In this embodiment, upper frame 6 comprises two top length links 23, cross beams 13 at the top, and cover plate 21 at the top. Likewise, lower frame 4 comprises two bottom length links 25, cross beams 13 at the bottom, and cover plate 21 at the bottom.

FIG. 2 a shows lengthwise spring 57 and pre-bent bow 51 which resist any compression force on guided p-diamond shoe 11; vertical springs 19 also resist external compression. Lengthwise spring 57 can be any type of spring, including a pre-bent bow. An external compression force can be exerted at any point on and between the section or vertices of upper frame 6 and lower frame 4—to store energy in the spring system. At the same time, an expansion force by the spring system will be exerted at any point on and between the areas of upper frame 6 and lower frame 4 (in particular at the toe during toe-off). Even though the compressive and expansive forces are not located in the same place, upper frame 6 will not tilt with respect to lower frame 4. This is the key feature of the guided p-diamond invention. The term “p-diamond” refers to the fact that the linkage comprises overlapping parallelograms and diamonds. The value of the invention is that this is the simplest structure using only hinges and a minimal-force guide to achieve this particular constraint of one degree of motion in a failsafe manner over the entire possible range of compression, and hinges are the cheapest, lightest, most robust means to achieve guiding of spring mechanisms in many applications.

Stops 44 and tethers 59 can be located so as to limit the motion of any link with respect to any other link. That is, stops 44 and tethers 59 may be located anywhere along any links, in any orientation, and there may be any number of these used in a particular embodiment. FIG. 2 actually depicts several variations of spring systems. FIG. 2 a shows lengthwise spring 57 (helical) acting between (1) the center cross bar 17 located between the particular cross beam 13 at the particular link hinge 16 connecting the outside (left) pair of diamond links 10 and (2) the center cross bar 17 between adjacent center length links 24. Note this second location could be anywhere along center length links 24. Tether 59 limits the amount of compression. FIG. 2 c shows vertical spring 19, an example of a spring acting in compression—directly resisting compression, and stop 44, stopping compression. Vertical spring 19 can be helical springs 48 or spiral helical springs 50 (which can compress to the wire thickness). In later figures herein, the zigzag schematic representation for helical springs is usually used to depict springs—for clarity. In fact, it is to be understood that any spring can be used, and it is far more likely that bow springs or leaf springs work better in these applications. Also, these springs can be used in tension as well as compression.

FIG. 2 c, the front view, shows the locations of vertical spring 19 and stop 44, located in this case between adjacent guided p-diamond linkages 9. In dashed lines, the location of center cross bar 17 is shown—for the case where a lengthwise spring 57 is used. Top view FIG. 2 d shows pre-bent bow 51 acting (in tension to resist compression) between two center cross bars 17. Also shown here is how cover plate 21 covers the frame work comprising top length link 23 and cross beams 13. Cover plate 21 is optional and upper frame 6 or lower frame 4 could alternatively be anything from a simple plate to a molded and highly optimized covered, pocketed framework.

It is understood with regard to all embodiments of linkage energy return sole 12 that any type of spring deemed useful can be used, and these may act in compression or tension between vertices or locations along links. Also, the anti-tilting constraint allows that a minimal number of vertical springs, even one, can suffice, and it ensures that both the heel and toe impact energy are returned through the runner's toe during the latter part of toe-off. Notably, single or multiple springs and stops, of any shape or type and between any locations on the mechanism elements, can be used to achieve any desired travel or compression from very little to the entire thickness of the unweighted sole. This full thickness may be only an inch or it may be six inches or more. Other spring options include tapered serpentine springs and air springs. By tapering a bow spring in a particular manner, it is possible to get just the right “hard” force curve where hard means the curve increases faster than a linear spring. Please refer to the discussion FIG. 12 for more examples of springs.

FIG. 3 a shows a side view of a guided p-diamond linkage 9 indicating how lengthwise springs with the proper hard force curve can be used to achieve a constant force curve. The vertical force exerted by pre-bent bow 51 can be expressed as the product of the mechanical advantage, MA, due to the diamond structure, times the horizontal force, Fx, exerted by lengthwise spring 57. If the length of diamond link 10 is Ld and the spring rate is K, then Fy=MA*K*x, where x is the change in length of pre-bent bow 51 as each diamond link 10 rotates an angle, a, from vertical—assuming a linear spring. Also, MA=(cos(a)/sin(a)) and x=Ld*sin(a). Thus, Fy=Ld*K*cos(a). By using a tension spring proportional to (1/cos(a)), one can achieve a constant force curve in which Fy remains approximately constant as guided p-diamond linkage 9 compresses under a load. Proper construction of a tapered pre-bent bow 51 will provide a hard curve which can be designed to give the desired force curve.

FIG. 3 b is a schematic side view of the linkage shoe 2 showing bow springs extending from lower frame 4 above guided p-diamond sole 8 to support upper frame 6 via shoe-plate posts 56. Other springs such as helical springs could be used instead. The advantage of these “external” springs which are not restricted to lie within the shoe sole is that the sole thickness can be smaller, and the springs, especially the bow springs, can be better optimized. Also, these external springs may be located anywhere on the outside perimeter of lower frame 4 including: only on the outside, in the front and the back, or only in the front. The structural constraint of the guided p-diamond linkage ensures that a spring located anywhere in the sole, e.g., only in the front, is loaded by a force acting anywhere on the sole, e.g., in the back.

FIG. 3 c shows a side view (with the front to the left) of guided bow linkage 365, to be used in a linkage energy return shoe. The sections of lower frame 4 and upper frame 6 between the two link hinges 504 (two of which are located in upper frame 6 and two of which are located in lower frame 4) form a parallelogram, along with the two vertical p-links 503. All four sides of this parallelogram are hingeably connected via four link hinges 504 to form a parallelogram linkage. Upper and lower frames 6 and 4 may extend beyond link hinges 504 for full support of runner's foot 1. Bow-link guide 362 is rigidly attached to lower frame 4, and it guides rolling bearing 353 along its length Rolling bearing 353 is hingeably attached to one end of bow link 361 which is hingeably attached at its other end to upper frame 6. As shown, this upper hingeable attachment uses the same link hinge 504 as the adjacent vertical p-link 503, but bow link 361 could be hingeably attached at another location on upper frame 6. Pre-bent bow 51 is hingeably attached between a forward location on lower frame 4 (again, as shown, happening to coincide with link hinge 504 for the forward vertical p-link 503) and rolling bearing 353. Ground plate curved toe 32 is shown as the front (left side in FIG. 3 c) end of lower frame 4. This optional feature allows the entire guided bow linkage 365 to more easily rock forward onto ground plate curved toe 32 during the end of toe-off.

Accordingly, as guided bow linkage 365 is compressed, the bottom of bow link 361 pushes rolling bearing 353 along bow-link guide 362, thereby stretching pre-bent bow 51 and thereby storing impact energy. At the end of compression, pre-bent bow 51 contracts, forcing upper frame 6 to lift all parts of runner's foot 1, including the toe, during toe-off. In this configuration upper frame 6 moves back and down as guided bow linkage 365 compresses and as vertical p-links 503 rotate clockwise. The opposite motion occurs during expansion. The fact that upper frame 6 is constrained to be parallel to lower frame 4 by the parallelogram nature of the linkage ensures that all the energy stored in pre-bent bow 51 acts to expand the front section of guided bow linkage 365, even if all the weight of the runner is on his toe at this time. The equivalent structural components shown in FIG. 3 c can be configured so that bow-link guide 362 and bow link 361 are located either in the top front, the top rear, the bottom front, or the bottom rear of guided bow linkage 365.

It should be understood that the particular configurations shown may be varied using various springs and locations of elements while still being covered by this embodiment of the invention, which is to combine a parallelogram-based sole linkage with a guided link to load a spring in sole compression. Other features, such as stops and tethers, and additional springs acting between the upper and lower plates can be included in the broad scope of this invention. Note that guided bow linkage 365 is a simplification of guided p-diamond linkage 9 in that guided bow linkage 365 is essentially the top half of guided p-diamond linkage 9. Notably, it reduces the number of links from nine to five while adding a guide.

FIGS. 4 a and 4 b show means to attach runner's foot 1 foot to linkage shoe 2. FIG. 4 a shows one of many possible strapping arrangements for shoe straps 22 to attach pre-existing shoe 34 to the front section of upper frame 6 and to the rear section of push-off frame 18 via buckles 36. FIG. 4 b shows toe cup 38 and heel cup 40 which can be used with or without pre-existing shoe 34 for the same attachment and which may still incorporate shoe straps 22. Heel bumper 39 and toe bumper 37 can also be optionally used to confine pre-existing shoe 34 to linkage shoe 2. In fact, toe cup 38 can include any number of attachments means to fixably attach pre-existing shoe 34 to upper frame 6 in such a manner that the runner's heel can lift above upper frame 6 during toe-off. That is, toe cup 38 can serve as a push-off means in and of itself without push-off frame 18. The rest of the sole of the linkage shoe is not shown here in FIGS. 4 a and 4 b, where push-off frame 18 is located at the level of the bottom of pre-existing shoe 34 or runner's foot 1, and it may extend a variable distance underneath pre-existing shoe 34 or runner's foot 1. Also, plate cover 21 here is shaped like an orthotic to conform to and give arch support to the bottom of runner's foot 1. Plate cover 21 could optionally be perforated to improve foot ventilation.

In contrast to the embodiments of FIG. 4 a and FIG. 4 b, FIG. 4 c shows an attachment means which obviates the push-off means—in that the heel of runner's foot 1 is directly attached to cover plate 21. In effect, ground plate curved toe 32 is the push-off means, by virtue of its shape and location. Here, ground plate rocker 30 with ground plate curved toe 32 allows runner's foot 1 to planter flex at its ankle—thereby lifting his heel and extending his leg/foot combination—even when runner's foot 1 is fixedly attached to attached along its full length from toe to heel to cover plate 21, and thereby to upper frame 6 of FIG. 1 via cover plate 21. Note that ground plate curved toe 32 is shaped and located just so, that guided p-diamond shoe 11 rocks forward onto ground plate curved toe 32 throughout toe-off- in such a manner the force line of the net force exerted by the runner's foot on the ground moves forward, in such a manner that this contact line always passes through the point of contact of ground plate curved toe 32 with the ground—resulting in a continuously forward rocking of ground plate rocker 30. Thus, a push-off means is not necessarily needed, although it may off some advantages.

FIG. 5 shows line-link side views of variations on the configuration of guided p-diamond linkage 9, namely asymmetric guided p-diamond linkage 545. This simplified “line-link” view will be used subsequently to illustrate the various alternative configurations of the linkages of the invention, because the essence of their functionality is thereby more easily seen. FIG. 5 a shows longer front diamond links 546, and FIG. 5 b shows short link 521 and long link 522, which can be used to control the longitudinal relative travel.

FIGS. 6 b (line-link side view) and 6 c (front view) show a half-height variation on guided p-diamond sole 8 wherein linkage pre-existing shoe 34 rests in a recessed structure, namely half-height foot plate 540 supported by half-height hangars 542 from the tops of guided p-diamond linkage 9 on either side of linkage pre-existing shoe 34. This feature reduces the height of runner's foot 1 above the ground, as compared with the design previously described in FIG. 1—shown again for easy comparison in FIG. 6 a. Note that this half-height feature can be used with any other of the linkage embodiments of this invention. It does, however, restrict the use of a pre-bent bow 51 to only the lower half of the height of guided p-diamond linkage 9. Before, separate pre-bent bows 51 could be used in both the top an bottom halves.

Another application of the guided p-diamond invention is bow shoe 202 shown in FIG. 7 (a side view) and FIG. 8 (a front view). It combines shin-level bow 240 and compressible guided p-diamond sole 8. All details such as the various springs are not shown here, but any of the features of the linkage shoe discussed earlier can be incorporated into the bow shoe. FIG. 7 a shows heel-strike, FIG. 7 b shows mid-stance with guided p-diamond sole 8 compressed, and FIG. 7 c shows toe-off. Energy return linkage 190, here shown in guided p-diamond sole 8, is equivalent to that shown in FIG. 2. Ankle-pivot supports 226 are rigidly attached on either side to lower frame 4—to support ankle-pivot housings 234 and ankle pivots 232. Stirrups 236 are pivotly connected to ankle-pivot support 226 by ankle pivot 232, and they prevent interference of the bow support section with runner's shin 3. Bow 240 is pivotly attached to stirrup 236 via lower bow hinge 242, and bow guide 238 is rigidly attached to stirrup 236. The top of bow 240 is pivotly attached to bow guide 238.

Cords 228 attach to a front and a rear side point on upper frame 6 at equal distances in front of and behind ankle-pivot support 226. Cords 228 extend up to be guided through the center of ankle-pivot housing 234 so as to minimize any torque exerted by cord 228 on bow guide 238 about ankle pivot 232. Cords 228, four in all—from the front and rear on both sides, extend further up to attach to upper bow hinge 244. Accordingly, when runner's foot 1 pushes down on upper frame 6 during foot-strike, bow 240 is loaded via cords 228. Since rear and front cords 228 are symmetrically positioned about ankle-pivot support 228 and since guided p-diamond sole 8 forces vertical compression, bow 240 is loaded by either or both heel and toe impact. This ensures that the full impact energy is returned through the runner's toe at toe-off. To keep bow 240 from flopping about, it is attached to shin strap 246 via shin slider 248 which is slidingly connected to the upper part of the telescoping bow guide 238.

There are several embodiments herein of an energy return linkage other than guided p-diamond linkage 9. These do not provide as full a constraint on the relative motion of the top and bottom sole plates as the guided p-diamond linkage, but they still have useful functionality for “full” energy return in walking or running. Most importantly, full energy return means that all heel and forefoot impact energy (neglecting friction losses) is returned for thrust, optimally in the latter part of toe-off. The signature feature of these embodiments is that they extend over the full or major length of the foot. Also, all of the features that apply to use of guided p-diamond linkage 9, such as push-off frame 18, apply to these other embodiments.

The next embodiment, shown in FIGS. 9, 10, and 11 is p-linkage 500. FIG. 9 a shows the four links that form a parallelogram (hence, the term “p”), namely top p-link 501, bottom p-link 502, and two vertical p-links 503, connected by link hinges 504. Diagonal spring 505 stores the energy of impact and compression, and forces the later expansion of p-linkage 500. Any of these linkages can be oriented backwards or forwards, but if the forward direction is to the left of FIG. 10, top p-link 502 moves backward with respect to bottom p-link 502 during impact. This has the advantage of reducing the effective line of force angle of the leg on the runner's center of mass, thereby reducing deceleration in the heel-strike period. Also, the opposite relative motion occurs in toe-off accelerating the runner forward more rapidly. Later, variations in the guided p-diamond configuration will be shown to achieve this same “slingshot” effect. It remains to be seen if this longitudinal relative motion is too large, because it cannot be precisely controlled as is the case for some of the next embodiments. FIG. 9 b shows a line-link side view of p-linkage 500. FIG. 9 c shows arbitrary length 4-link linkage 510, which recognizes that there may be good design reasons for the lengths of a 4-link linkage to have the somewhat arbitrary values of arbitrary length links 507. The main point of this patent is that 4-bar linkages (in combination with additional links or other 4-link linkages) permit control of the motion and orientation of a runner's foot. Exact values or symmetries may not be necessary or even recommended. This statement makes it clear that the relative motions of upper frame 6 and lower frame 4 only need to remain substantially parallel (but not precisely parallel) during stance for this patent to apply. FIGS. 10 a, 10 b, and 10 c are schematic side views of p-linkage 500 while running. FIG. 10 a shows heel-strike, FIG. 10 b shows mid-stance with guided p-diamond sole 8 compressed, and FIG. 10 c shows toe-off.

FIG. 11 shows three views of p-linkage shoe 525. Side-view FIGS. 11 a show p-linkage shoe 525 expanded. FIG. 11 c is a front view and FIG. 11 b is a top view. P-linkage shoe 525 comprises top p-link 501, bottom p-link 502, and two vertical p-links 503, all hingeably interconnected at link hinges 504 to form a 4-bar (parallelogram) linkage called p-linkage 500. The two vertical p-links 503 rotate as p-linkage 500 compresses. In the particular design shown in FIG. 11, two p-linkages 500 are on either side, are rigidly bridged by cross beams 13, and are optionally covered by cover plates 21 on the top and the bottom. Cover plate 21 need not cover the entire area of lower frame 4; it could simply be made of a durable material such as vibram or hard rubber bonded to the length and cross beam elements of bottom p-link 502. Top p-link 501 and bottom p-link 502 optionally extend beyond p-link hinges 504 on either end, but the functional parts for p-linkage 500, those which cause the critical constraint p-linkage 500 to maintain top p-link 501 and bottom p-link 502 parallel, require only the sections between p-link hinges 504. Bottom p-link 502 may comprise ground plate rocker 30 and ground plate curved toe 32 of FIG. 4.

FIG. 11 a shows diagonal spring 505 which resists compressive force on p-linkage shoe 525. External compression force can be exerted at any point on and between the section or vertices of p-linkage 500—to store impact energy in the spring system. At the same time, an expansive force by the spring system will be exerted between any opposite points on top p-link 501 and bottom link 502 (in particular at the toe) throughout take-off. That is, even though the compressive and expansive forces are not located in the same place, p-linkage 500 will remain a parallelogram. As was true for the discussion of the guided p-diamond linkage 9, any types of stops, tethers, and springs can be wherever on p-linkage 500, provided they resist or limit its compression. That is, stops, tethers, and springs may be located anywhere along any links, at any orientation, and in any number. The top and front views FIG. 11 b and FIG. 11 c show the locations of the various elements of p-linkage 500, and the discussion of guided p-diamond linkage 9 of FIG. 2 applies equivalently here.

FIG. 12 shows examples of various springs that can be used to store energy in linkage energy return sole 12. FIG. 12 a shows leaf spring 551, torsion spring 550, spiral helical spring 50, bow spring 52, and bending spring 552. FIG. 12 b shows that double leaf spring 554 is equivalent to two leaf springs 551 rigidly attached as indicated by arrows 558. FIG. 12 c shows a side view of conical spring 553, and FIG. 12 d shows its top view. Again, any of these or other well known springs may be connected hingeably or rigidly between only location on energy return sole 12. For example, bow spring 52 can be used in tension or compression between its ends, or it can be used in tension or compression between its center and its two ends, which ends (and/or which top) could be attached rigidly, pivotly, or slidingly to location on in linkage energy return sole 12. This is also true for all embodiments herein.

FIG. 13 shows line-link side views of stretched-p linkage 177 which comprises p-linkage 500 of FIG. 11 with additional links. FIG. 13 a shows stretched-p linkage 177 expanded and FIG. 12 b shows it compressed. Stretched-link extensions 173 are added on one (FIG. 12 c) or both ends of top p-link 501 to form entire upper link 176 and, likewise, to form entire lower link 175. Two stretched links 171 are hingeably interconnected via stretched hinges 172 and are hingeably connected to stretched-link hinges 174 (in stretched-link extensions 173) on entire lower link 175 and entire upper link 176. Diagonal spring 505, between the front one of stretched hinge 172 and the rear one of stretched hinge 172, is stretched as stretched-p linkage 177 is compressed. In FIG. 13 c, diagonal spring 505 is hingeably connected between stretched hinge 172 and the rear, upper link hinge 504—in that stretched links 171 are used only in the front (left). Again, diagonal spring 505 may be any type of spring, and springs may be used (via rigid, sliding, or hingeable attachments) between any locations on p-linkage 500. The applies to all the embodiments herein, as well.

FIG. 14 shows line-link side views of another embodiments of 2-p linkage 511, e.g. in FIG. 14 a where diagonal springs 505, and other springs such as vertical spring 19 can be used. Here, two p-linkages 500 share a common link, mid-p-link 512, and the relative longitudinal motion of the upper and lower links can be precisely controlled (about zero), either with different forces for upper and lower diagonal springs 505, e.g., asymmetric diagonal spring 518, or by using asymmetric vertical p-link 516 (of different length). Both of these control strategies are shown in FIG. 14 b of asymmetric 2-p linkage 515. FIG. 14 c shows thin-toe 2-p linkage 560 with short vertical links 559 (short as compared with vertical links 503)—to make the front sole thickness of the various embodiments of 2-p linkage 560 thinner than the back. It is to be understood that this same feature, namely using shorter links in the front of linkage shoe 2, can be used in any embodiment of the invention. It means that the upper and lower plates of the sole are not always parallel, but that is not the fundamental goal of the invention. The fundamental goal of the invention is to constrain the motion of the upper plate so that the maximum possible heel impact energy is returned through the toe in toe-off.

FIGS. 15 a and 15 b show line-link side views of hanging p-linkage 526. FIG. 30 a shows the expanded state, and FIG. 30 b the compressed state. Here, diagonal spring 505 connects at either end to p-extension hinges 509 at the ends of p-link extensions 508 which are rigidly attached to top p-link 501 and bottom p-link 502. The advantage of this embodiment is that if pre-bent bow 57 (e.g. in FIG. 1) is used for diagonal spring 505, its shape can be more symmetric and more easily optimized.

In summary, this “linkage energy return sole 12” invention includes several energy return linkages, all of which extend the full length of the shoe and all of which constrain the upper and lower plates or frame of the sole to move in a constrained manner with respect to one another so that the runner's toe is lifted in toe-off by both stored heel impact and toe impact energy and so that this thrust does not occur prematurely—as is the case for prior art energy return shoes in which the heel spring expands prematurely and wastefully. Note that the orientation of the “vertical motion only” constrained linkages of this invention can be rotated ninety degrees about the vertical axis so that the vertical links open laterally rather than longitudinally, provided that the effective “width” of this lateral linkage be the full length of the shoe sole. It is to be further understood within the full scope of the invention that any combination of the linkages described herein can be used together in any orientation to realize the invention goal of full energy return. And, any of the features described in a particular embodiment of the invention can be used in other embodiments of the invention.

While several forms of the invention have been shown and described, other forms will now be apparent to those skilled in the art. Therefore, it will be understood that the embodiments shown in the drawings and described above are merely for illustrative purpose, and are not intended to limit the scope of the invention which is defined by the claims which follow as interpreted under the principles of patent law including the doctrine of equivalents. 

1. In a shoe a linkage energy return shoe sole for walking, running, and jumping by a wearer comprising an upper sole plate, a lower sole plate, a combined energy return linkage comprising one or more energy return linkages, wherein each said energy return linkage comprises at least one 4-bar linkage comprising four links hingeably interconnected at link hinges, wherein each link rotates in the longitudinal front-to-back plane formed by a vertical line and by a line extending from the front to back of said linkage energy return shoe sole, a spring system to store and return energy of compression of said linkage energy return shoe sole, wherein said spring system comprises at least one spring, wherein each one spring may act between any two locations on said combined energy return linkage, wherein the range action of each one spring may be restricted by various types of stops, and a foot attachment means to attach said linkage energy return shoe sole to the foot of said wearer, wherein said foot may be that of a person, a foot prosthesis, or a robot.
 2. The linkage energy return shoe sole of claim 1 wherein said combined energy return linkage comprises links of various lengths, wherein opposing said links may or may not be parallel, wherein said upper sole plate may or may not be parallel to said lower plate, wherein the thickness of the front of said linkage energy return shoe sole may less or more than the thickness of the back of said linkage energy return shoe sole.
 3. The linkage energy return shoe sole of claim 1 wherein said upper sole plate comprises a push-off means which allows said wearer to flex his metatarsal joint and push off his toe during toe-off.
 4. The linkage energy return shoe sole of claim 1 wherein said bottom sole plate comprises a curved bottom wherein said curved bottom which comprises a curled toe, wherein said bottom sole plate is rigid.
 5. The linkage energy return shoe sole of claim 3 wherein said push-off means comprises a push-off frame hingeably connected to said upper sole plate by a toe hinge and extending rearward, and fixedly attached to the rear foot of said wearer, wherein both the heel of said wearer and said push-off frame are free to rotate about said toe hinge and away from the rear section of said upper sole plate.
 6. The linkage energy return shoe sole of claim 3 wherein said push-off means comprises a particular location and shape of said curled toe, wherein said linkage energy return shoe sole rocks forward throughout toe-off about the rolling bearing formed by said curled toe.
 7. The linkage energy return shoe sole of claim 1 wherein said combination linkage comprises one or more guided p-diamond linkages each of which comprises nine links further comprising four diamond links, two end links, a top length link, a center length link, a bottom length link, wherein said nine links are hingeably connected by link hinges, wherein said top length link is rigidly attached to said upper sole plate, and said bottom length link is rigidly attached to said lower sole plate, wherein the four said diamond links are hingeably interconnected by said link hinges to form a diamond shape, with two top links and two bottom links, wherein two interconnecting diamond links, one of which is a bottom link, are called outside diamond links because they face away from the center of said p-diamond and the other two diamond links are called inside diamond links, wherein a top link hinge connecting the top two said diamond links is hingeably connected to said top length link, wherein a bottom link hinge connecting the bottom two diamond links is hingeably connected to said bottom length link, wherein the two said outside diamond links are hingeably connected by a link hinge called the outside link hinge, and the two inside diamond links are hingeably connected by a said link hinge called the inside link hinge, wherein said top length link is also hingeably connected to one of said end links, and said bottom length is also hingeably connected to the other one of said end links, wherein said end links are hingeably interconnected by a link hinge called the end center link hinge, wherein said center length link is connected to said inside link hinge and said end center link hinge, wherein the overall configuration of said nine links of said p-diamond linkage (for the particular but not the required case when all diamond links and end links are the same length) is two parallelograms and a diamond which overlap one another and that is why the invention is referred to as a p-diamond, wherein the two said outside diamond links constrain said p-diamond to compress in such a manner that said top length link remains parallel to said bottom length link which means said p-diamond compresses without tilting, and a mid-link front vertex guide rigidly extending along and from said center length link to make a key constraint on said outside link hinge to move within and along said mid-link front vertex guide, along the continuation line extending along the length of said mid length link, wherein said upper sole plate is constrained to move exactly vertically (with no tilting) with respect to said lower sole plate for the case when all of said diamond links and said end link have the same lengths, wherein said upper sole plate is constrained to move in a prescribed trajectory with the designed vertical travel with controlled tilting with respect to said lower sole plate for the case when all of said diamond links and said end links do not have the same lengths which is the case when the thickness of the front of said linkage energy return shoe sole is less than the thickness of back of said linkage energy return shoe sole.
 8. The linkage energy return shoe sole of claim 7 wherein said spring system comprises one or more horizontal springs acting said inside link and said center length link, wherein said one or more horizontal springs may be attached at any location along the length of said center length link, wherein said one or more horizontal springs may be one of many types such as helical springs, leaf springs, or curved bow springs.
 9. The linkage energy return shoe sole of claim 8 wherein said horizontal spring has a force curve which allows the vertical force curve of said spring system to be approximately constant over the compression of said p-diamond.
 10. The linkage energy return shoe sole of claim 7 wherein said upper sole plate comprises a half-height sole comprising half-height hangars which extend downward from the level of the top of said top links and the level of the top of the top one of said end links to a level of approximately one-half that height—to fixedly attach to a half-height foot plate, thereby reducing the effective height of said linkage energy return shoe sole by a half and improving lateral sole stability.
 11. The linkage energy return shoe sole of claim 1 wherein said combination linkage is a p-linkage comprising four p-links which hingeably interconnect via said link hinges to form a parallelogram.
 12. The linkage energy return shoe sole of claim 1 wherein said combination linkage is a 2p-linkage comprising seven 2p-links which form two parallelograms with a shared link.
 13. The linkage energy return shoe sole of claim 11 wherein said a p-linkage comprises a stretched-p linkage comprising one or pairs of stretched links hingeably interconnected at a stretched link hinge and hingeably connected to a top and a bottom left-most of said link hinges on the front side or on the back side, or on both front and back sides, wherein a stretched spring between one of stretched hinge and another stretched hinge resists compression of said p-linkage, wherein a stretched spring acts between said stretched hinge and an opposing one of said link hinges for the case when only one said pair of stretched links is used.
 14. The linkage energy return shoe sole of claim 11 wherein said p-linkage comprises a hanging-p linkage comprising one or more p-extension hinges on the ends of p-link extensions which rigidly extend from front and back said p-links outward and toward the height center (diagonally downward for an upper said p-link and diagonally upward for a lower said p-link), wherein a lengthwise said spring is hingeably connected between the front and back said p-extension hinges, wherein interference of lengthwise said spring with other elements of said hanging-p linkage is reduced during compression of said hanging-p linkage.
 15. The linkage energy return shoe sole of claim 1 which further comprises a bow shoe for use by a wearer, wherein said spring system comprises a bow spring located above said upper sole plate and hingeably connected to said upper sole plate, a leg attachment means for attaching said bow spring to the leg of said wearer, a suspension system connecting the top of said bow spring to said lower sole plate, wherein the force of both the wearer's toe and heel cause said bow spring to be loaded throughout foot-strike, wherein heel impact energy is not returned prematurely at the beginning of to push-off, but rather is returned optimally during toe-off during the latter part of push-off.
 16. The linkage energy return shoe sole of claim 12 wherein said suspension system comprises one or more ankle-pivot supports rigidly attached to said lower sole plate and extending around and above the level of the foot of said wearer, one or more ankle-pivot housings rigidly attached to said ankle-pivot support and housing an ankle pivot, one or more cords attached to said upper sole plate and passing around the foot of said wearer and through said ankle-pivot housings, and a cord guide to constrain said cords to the location of said ankle-pivot.
 17. The linkage energy return shoe sole of claim 12 wherein said suspension system further comprises a shin-level bow spring assembly comprising a bow spring pivotly attached to said ankle-pivot housing, a bow guide pivotly attached to said ankle-pivot housing and to the top of said bow spring, wherein said bow guide changes length telescopically, a shin slider slidingly attached to the top of said bow guide, and a shin strap for attaching said shin slider to the shin of said wearer, wherein said cords extend to connect to the top of said bow spring, wherein the impact force of said wearer's foot on said shoe plate loads said bow spring via said cords.
 18. A guided p-diamond shoe sole for walking, running, and jumping by a wearer comprising a guided p-diamond sole comprising an upper sole plate, a lower sole plate, one or more guided p-diamond linkages each of which comprises nine links further comprising four diamond links, two end links, a top length link, a center length link, a bottom length link, wherein said nine links are hingeably connected by link hinges, wherein said top length link is rigidly attached to said upper sole plate, and said bottom length link is rigidly attached to said lower sole plate, wherein the four said diamond links are hingeably interconnected by said link hinges to form a diamond shape, with two top links and two bottom links, wherein two interconnecting diamond links, one of which is a bottom link, are called outside diamond links because they face away from the center of said p-diamond and the other two diamond links are called inside diamond links, wherein a top link hinge connecting the top two said diamond links is hingeably connected to said top length link, wherein a bottom link hinge connecting the bottom two diamond links is hingeably connected to said bottom length link, wherein the two said outside diamond links are hingeably connected by a link hinge called the outside link hinge, and the two inside diamond links are hingeably connected by a said link hinge called the inside link hinge, wherein said top length link is also hingeably connected to one of said end links, and said bottom length is also hingeably connected to the other one of said end links, wherein said end links are hingeably interconnected by a link hinge called the end center link hinge, wherein said center length link is connected to said inside link hinge and said end center link hinge, wherein the overall configuration of said nine links of said p-diamond linkage (for the particular but not the required case when all diamond links and end links are the same length) is two parallelograms and a diamond which overlap one another and which is why the invention is referred to as a p-diamond, wherein the two said outside diamond links constrain said p-diamond to compress in such a manner that said top length link remains parallel to said bottom length link which means said p-diamond compresses without tilting, and a mid-link front vertex guide rigidly extending along and from said center length link to make a key constraint on said outside link hinge to move within and along said mid-link front vertex guide, along the continuation line extending along the length of and from said center length link, wherein said upper sole plate is constrained to move exactly vertically (with no tilting) with respect to said lower sole plate for the case when all of said diamond links and said end link have the same lengths, wherein said upper sole plate is constrained to move in a prescribed trajectory with the designed vertical travel with controlled tilting with respect to said lower sole plate for the case when all of said diamond links and said end links do not have the same lengths which is the case when the thickness of the front of said linkage energy return shoe sole is less than the thickness of back of said linkage energy return shoe sole, a spring system to store and return energy of compression of said guided p-diamond sole, wherein said spring system comprises at least one spring and wherein each one spring may act between any two locations on said guided p-diamond linkage and wherein the range action of each one spring may be restricted by various types of stops, and a foot attachment means to attach shoe sole to the foot of said wearer, wherein said foot may be that of a person, a foot prosthesis, or a robot. 